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Additional reflections seemingly leading to a tetragonal fivefold supercell have been observed in a number of melilites. A careful examination of the collected intensity data reveals that this feature is due to the coexistence of two twin domains related by a (120) twin plane. Reflections of the first domain (I) with h(b)(2) + k(b)(2) = 5n overlap those of the second domain (II) when both the following additional conditions are verified: -h(b) + 2k(b) = 5n and 2h(b) + k(b) = 5n. Indices of the superimposed reflections are h(b,I) k(b,I) l(b,I) for the first domain, and h(b,II) = 3/5h(b,I) + 4/5k(b,I), k(b,II) = 4/5h(b,I) - 3/5k(b,I), l(b,II) = l(b,I) for the second domain. The non-crystallographic pseudosymmetry in the melilite structure is discussed.

The syntheses of the 4-coordinate Tp'MCl complexes (where M = Fe (1), Mn (2); and Tp' = hydrotris(3-isopropyl-4-bromopyrazolyl)borate) are described. The single-crystal X-ray structures show that the metal centers have distorted tetrahedral coordination. Analogous reaction of CrCl(2)(MeCN)(2) with TlTp' gave Cr(kappa(3)-Tp')(kappa(2)-Tp') (3) as the initial product. The 5-coordinate structure was assigned by single-crystal X-ray crystallography, and it was found that the kappa(3) ligand had isomerized to hydro(3-isopropyl-4-bromopyrazolyl)(2)(5-isopropyl-4-bromopyrazolyl)borate). 3 is labile in solution: in pentane it slowly converts to the 6-coordinate isomer Cr(kappa(3)-Tp')(2) (4), whose structure was determined by X-ray crystallography. In 4 both ligands are isomerized. Both 3 and 4 display Jahn-Teller distorted structures expected for high-spin d(4) configurations. Variable temperature magnetic susceptibility measurements confirm that 1, 2, and 3 all have high-spin electronic configurations in the range 5-300 K. In benzene solution 3 decomposes; one product [Cr(kappa(3)-Tp')(2)](+)[Tp'](-) (5), was identified by X-ray crystallography. 5 contains a pseudooctahedral Cr(III) cation with both ligands in the isomerized form and an uncoordinated Tp' ligand as counterion. Mechanistic studies reveal that this reaction is light rather than heat induced. IR spectroscopy is utilized to confirm the ligand hapticity in all complexes from the value of nu(B)(-)(H), and comparison is made with similar compounds.

This article reviews current trends in undergraduate and postgraduate medical education and speculates on the future in the new millennium.

Relatively few data exist on atrial natriuretic peptide (ANP) characteristics in Type 2 diabetes mellitus (DM). Therefore, plasma immunoreactive ANP concentrations were measured before and for 4 h following the ingestion of a physiological mixed meal in 8 newly diagnosed, normotensive, normoalbuminuric, patients with Type 2 DM and 6 normotensive, non-diabetic controls. In patients with Type 2 DM, basal plasma ANP concentrations were 4.0 +/- 2.0 and not significantly changed following ingestion of the meal, with peak levels of 4.9 +/- 2.8 pmol l(-1). Non-diabetic controls had higher basal plasma ANP concentrations, 8.7 +/- 3.4 pmol l(-1) (p < 0.05), significantly increasing to a peak of 11.9 +/- 6.3 pmol l(-1) at 30 min post meal. Extracellular fluid volume (ECV) was not different between diabetic patients and controls (15877 +/- 2679 vs 13668 +/- 1792 ml3). Glomerular filtration rate (GFR) (isotopic clearance corrected for body surface area) was elevated in diabetic patients (mean +/- SD) 130 +/- 39 vs 98 +/- 10 ml min(-1), p < 0.05). For the DM subjects, basal ANP levels were negatively correlated with GFR (rs - 0.74, p < 0.05) and effective renal plasma flow (ERPF) (rs - 0.8, p < 0.05). We conclude that patients with Type 2 DM demonstrate reduced basal plasma ANP concentrations which are inversely correlated to renal function. In contrast to non-diabetic controls, ANP in Type 2 DM does not rise in response to feeding.

Objective: Cushing's syndrome in childhood and adolescence is rare. We analysed the clinical presentation, investigation, management and therapeutic outcome in 12 paediatric patients with Cushing's syndrome., Design: Retrospective review of case notes., Patients: Twelve patients, 7 males and 5 females, aged 7.6-17.8 years with Cushing's syndrome who were admitted to St Bartholomew's Hospital between 1978 and 1993, were studied. Aetiologies of the Cushing's syndrome patients were: Cushing's disease (9), adrenal adenoma (1), nodular adrenocortical dysplasia (1) and ectopic ACTH syndrome (1). One further male patient, aged 17.8 years who presented with Nelson's syndrome after bilateral adrenalectomy for Cushing's disease in 1978, is described., Measurements: Presenting symptoms, endocrine tests for hypercortisolism, imaging studies, simultaneous bilateral inferior petrosal sinus sampling and therapeutic strategies are discussed., Results: The dominant clinical features were obesity, short stature, virilization, headaches, fatigue and emotional lability. Investigations confirmed Cushing's syndrome by demonstrating absent cortisol circadian rhythm and impaired suppression on low dose dexamethasone test and differentiated Cushing's disease from other aetiologies by high dose dexamethasone and hCRH tests. In Cushing's disease, pituitary CT scan identified a microadenoma in 4 out of 9 subjects. In 5 of the 9 patients (3 with a normal pituitary CT, 2 with a suggested microadenoma), a pituitary MRI scan was performed and confirmed the CT findings. Inferior petrosal sinus catheterization for ACTH in 4 patients confirmed excess pituitary ACTH secretion, correctly lateralizing the tumour in all cases. Cushing's disease was treated by transsphenoidal surgery alone in 6 patients and combined with pituitary irradiation in 3 patients. Of these 9 patients, 7 are cured and 2 are in remission. The patient with Nelson's syndrome is cured after total hypophysectomy., Conclusions: This series describes the clinical features, aetiologies and management of juvenile Cushing's syndrome. Investigation with low and high-dose dexamethasone suppression tests and hCRH test identified the aetiology in each case. Collaboration between paediatric and adult endocrine units together with an experienced neurosurgeon and a radiotherapist contributed to the successful therapeutic outcome of these patients.

Objective: Insulin-like growth factor-I is the mediator of many of the actions of GH and is a potent metabolic regulator. Recombinant IGF-I (rhIGF-I) is of potential value in the treatment of syndromes associated with either GH or insulin resistance. This study was designed to assess the effects of subcutaneous (s.c.) rhIGF-I on anterior pituitary function., Design: Double-blind, placebo controlled, randomized cross-over study. The interval between investigations was 2 weeks., Subjects: Twelve normal volunteers received on one occasion a single s.c. dose of 40 micrograms/kg rhIGF-I and on the other, placebo., Measurements: Circulating levels were measured, over 24 hours, of GH, LH, FSH, PRL, TSH, cortisol, ACTH, glucose, IGF-I, IGF-II, insulin, C-peptides; IGF binding proteins by Western ligand blotting; total IGF bioactivity using FRTL-5 thyroid cells; and glucose by the glucose oxidase method., Results: Recombinant IGF-I increased AUC for plasma IGF-I, measured by radioimmunoassay (rhIGF-I mean 7065 +/- SEM 33 vs 3895 +/- 204 micrograms/l, P < 0.0001) and IGF bioactivity (22.5 +/- 3.4 vs 14.2 +/- 1.8 U/ml, P < 0.001) but plasma IGF-II fell (9308 +/- 403 vs 11052 +/- 451 micrograms/l, P < 0.0001). There was no biochemical or clinical evidence of hypoglycaemia and no difference in mean glucose levels. No difference existed in AUC for GH, LH, FSH, ACTH and cortisol between rhIGF-I and placebo; additionally, pulse number and amplitude for GH and LH were unaffected. TSH fell following rhIGF-I (33.0 +/- 3.36 vs 42.5 +/- 5.98 mU h/l, P = 0.01). Both mean plasma C-peptide (0.73 +/- 0.06 vs 0.91 +/- 0.05 nmol/l, P = 0.03), and insulin (10.81 +/- 1.02 vs 15.36 +/- 1.18 mU/l, P = 0.03) were lower following rhIGF-I. There was no change in IGFBPs., Conclusion: A single injection of 40 micrograms/kg of subcutaneous rhIGF-I does not cause hypoglycaemia. IGF bioactivity was increased without inhibition of GH secretion. The only change observed in anterior pituitary function was a fall in plasma TSH.

Objective: Current studies reveal little regarding the inception of exercise-induced LH changes during physical training. This study aimed to assess the susceptibility of the hypothalamic-pituitary axis to the acute physical stress of exercise in untrained, physically inactive women. The acute effects of submaximal endurance exercise upon the pulsatile LH secretion in the follicular phase were compared with those accompanying leisurely strolling for a similar time period., Subjects: All subjects were eumenorrhoeic, as determined by biphasic temperature patterns, detection of the urinary LH surge, and mid-luteal serum progesterone levels. Subjects were not physically active and had little history of strenuous exercise (VO2max = 38.0 +/- 1.8) (mean +/- SEM) ml/kg/min)., Design: All women completed a 13.5-hour pulsatility test which included three consecutive 20-minute runs on a treadmill at 50, 60 and 70% of the subjects' maximum oxygen uptake (n = 16). Six of these same subjects completed a separate test on another occasion in which one hour of leisurely strolling was substituted for exercise. Blood was sampled every 10 minutes via an indwelling cannula for 4.5 hours before and 8 hours after one hour of exercise and or strolling., Measurements: A pulse algorithm (Pulsar) was used to quantify LH pulse characteristics., Results: Exercise produced no significant effects upon LH pulse frequency or mean serum LH concentration. However, exercise of moderate intensity caused a significant increase in LH pulse amplitude (P < 0.05). Strolling produced no significant changes in LH secretion., Conclusion: Acute exercise of moderate intensity in the follicular phase of untrained women is an insufficient stimulus to inhibit the GnRH pulse generator in the post-exercise period, yet may produce a slight stimulatory effect on the amount of LH released per pulse.

It has been suggested that the well-documented hypercortisolaemia found in a proportion of patients with severe depression occurs either in response to excessive secretion of corticotrophin-releasing hormone-41 (CRH-41) from the hypothalamus, or as a consequence of up-regulation of pituitary CRH-41 receptors. The attenuation of the normal ACTH response to CRH-41 in these subjects is thought to result from inhibition of corticotrophin secretion by elevated cortisol levels. We tested these hypotheses by examining ACTH responses to metyrapone, an 11 beta-hydroxylase inhibitor which blocks the formation of cortisol, followed by CRH-41 in 15 severely depressed in-patients diagnosed according to DSM-IIIR criteria. Patients were assigned to two groups according to their response to overnight administration of 1 mg dexamethasone: suppressors (8) and nonsuppressors (7). A third group consisted of 6 healthy matched controls. Metyrapone 750 mg was given 4-hourly for 24 h and samples were taken for cortisol and ACTH. Six of the original 15 patients (3 from each group) were given a bolus dose of 100 micrograms human CRH-41 intravenously after 24 h of metyrapone, and ACTH levels were measured over 2 h. Falls in circulating cortisol in response to metyrapone were similar in all three groups. However, we found exaggerated rises in ACTH amongst the nonsuppressors, as compared to the suppressors and the control group, after metyrapone.(ABSTRACT TRUNCATED AT 250 WORDS)

Objective: To analyse the clinical and biochemical effects of metyrapone in the treatment of Cushing's syndrome., Design: An evaluation of the standard clinical practice at one institution., Patients: Ninety-one patients with Cushing's syndrome: 57 pituitary-dependent Cushing's disease, 10 adrenocortical adenomas, six adrenocortical carcinomas and 18 ectopic ACTH syndrome., Measurements: The acute response to metyrapone was assessed by measuring cortisol, 11-desoxycortisol and ACTH at 0, 1, 2, 3, 4 hours after a test dose of 750 mg of metyrapone. The longer-term effect of metyrapone was judged by measuring serum cortisol at 0900, 1200, 1500, 1800, 2100 and sometimes 2400 h and calculating a mean., Results: A test dose of 750 mg of metyrapone decreased serum cortisol levels within 2 hours in all groups of patients and this effect was sustained at 4 hours. At the same time, serum 11-desoxycortisol levels increased in all patients, while plasma ACTH increased in patients with pituitary Cushing's disease and the ectopic ACTH-syndrome. Fifty-three patients with Cushing's disease were followed on short-term metyrapone therapy (1 to 16 weeks) before other more definitive therapy. Their mean cortisol levels (median 654 nmol/l, range 408-2240) dropped to the target range of less than 400 nmol/l in 40 patients (75%) on a median metyrapone dose of 2250 mg/day (range 750-6000). Metyrapone was given long term in 24 patients with Cushing's disease who had been given pituitary irradiation, for a median of 27 months (range 3-140) with adequate control of hypercortisolaemia in 20 (83%). In 10 patients with adrenocortical adenomas and six with adrenocortical carcinomas, metyrapone in a median dose of 1750 mg/day (range 750-6000) reduced their mean cortisol levels (median 847 nmol/l, range 408-2000) to less than 400 nmol/l in 13 patients (81%). In 18 patients with the ectopic ACTH-syndrome the 'mean cortisol levels', obtained from five or six samples on the test day (median 1023 nmol/l, range 823-6354) were reduced to less than 400 nmol/l in 13 patients (70%), on a median dose of 4000 mg/day (range 1000-6000). Reduction of cortisol levels was clearly associated with clinical and biochemical improvement. The medication was well tolerated. Transient hypoadrenalism and hirsutism were unusual but were the most common side-effects., Conclusions: In our experience metyrapone remains a most useful agent for controlling cortisol levels in the management of Cushing's syndrome of all types.

We have employed an acute explant system of the rat hypothalamus in vitro, as previously described, to examine the role of calcium and calmodulin in the release of corticotrophin-releasing hormone-41 (CRH-41). Release of CRH-41, as determined by radioimmunoassay, was stimulated in a dose-dependent manner by the membrane-depolarizing agents KCl and veratridine. Stimulation was also observed with the calcium ionophore A23187. The calcium channel blocker verapamil (1-100 mumol/l) inhibited both KCl- and veratridine-induced release in a dose-dependent manner (maximum inhibition of 75% and 60% respectively), thus providing further evidence that calcium entry is required for secretion of CRH-41 following membrane depolarization. Trifluoperazine (1-100 mumol/l), an inhibitor of calmodulin-calcium interaction, decreased both KCl- and veratridine-evoked CRH-41 secretion in a dose-dependent fashion (maximum inhibition of 50% and 30% respectively). Similarly, phenytoin, a calmodulin-dependent kinase inhibitor, in the concentration range of 1-100 mumol/l, also decreased depolarization-induced CRH-41 release in a dose-dependent manner. The basal release of CRH-41 was unaffected by either treatment. Finally, both calmodulin inhibitors (10 mumol/l) decreased CRH-41 release induced by the calcium ionophore A23187 (10 mumol/l). These data provide evidence for the role of calcium in membrane depolarization-induced stimulus-secretion coupling of rat hypothalamic CRH-41. Furthermore, inhibition of the stimulatory responses by two separate classes of calmodulin inhibitors suggests a role for calmodulin, at least in part, in this process.

OBJECTIVE To determine the long-term effects of external beam megavoltage radiotherapy (RT: 4500 cGy via three portals at 180 cGy or less total daily dose) on endocrine function in prolactinomas. DESIGN Longitudinal study following radiotherapy with periodic re-assessment at regular intervals, at least 2 months off dopamine agonist therapy. PATIENTS Thirty-six female patients, age range 19-50 years, with either macroprolactinomas (12 patients) or microprolactinomas (24 patients), but without significant suprasellar extensions. MEASUREMENTS Clinical appraisal, and anterior and posterior pituitary assessment: basal levels at yearly intervals or less, with dynamic screening with TRH, LHRH and hypoglycaemic stimulation every 2-3 years. RESULTS Before RT, serum prolactin (PRL) levels ranged from 1150 to 34,000 mU/l; after RT (mean 8.5 years, range 3-14), serum PRL fell to normal (i.e. less than 360 mU/l) in 18 of the 36 patients (50%), and to just above the normal range (378-780 mU/l) in a further 10 (28%). Two patients had PRL levels at their last follow-up higher than those at presentation, with one patient showing evidence of tumour recurrence on CT scan. A total of eight of the 36 patients (23%) developed post-RT gonadal deficiency by the end of follow-up at 8 +/- 3.1 years (+/- SD, range 3-11), but six were aged over 40 years at that time. GH deficiency was frequent, occurring in 94% of patients, usually from 2 to 3 years post-RT, while TSH deficiency and reduced ACTH reserve was uncommon (each 14%), and occurred later. In the subgroup of 12 patients with macroprolactinomas, results were broadly comparable. CONCLUSIONS Megavoltage RT produces a progressive fall in serum prolactin in the great majority of patients with prolactinomas, with a relatively low incidence of TSH or ACTH deficiency. As it is now clear that dopamine agonist therapy alone provides sufficient management for microprolactinomas, RT may be used for the long-term control of macroprolactinomas, together with interim dopamine agonist therapy. It allows pregnancy to be safely undertaken but, in view of the delayed onset of gonadal deficiency, its administration should be timed with respect to the desired onset of conception in women.

The reports of the effect of calcitonin on pituitary function are confusing and often refer to uncontrolled studies. We have now carried out a double-blind placebo-controlled trial of intravenous and subcutaneous salmon calcitonin on anterior pituitary function in 17 healthy volunteers. Visual analogue scores for the nausea and vomiting seen after salmon calcitonin correlated with the rise in ACTH and, secondarily, cortisol. Calcitonin had no effect on growth hormone, prolactin, thyrotrophin, luteinizing hormone or follicle stimulating hormone. It is concluded that the stimulation of ACTH secretion following a single dose of salmon calcitonin is probably the result of the stress of nausea rather than a direct effect on the pituitary.

The pro-opiomelanocortin gene is widely expressed in human tissues, although both transcriptional initiation sites and regulation appear to be tissue specific. In order to determine how promoter and enhancer choice is effected, we have studied the methylation pattern of the gene in a number of normal tissues, tumours and cell lines. Variability of this pattern was observed in the 5'-flanking DNA, particularly at the HpaII site located at -304 bp upstream from the pituitary CAP site. This site was generally methylated in tissues likely to express the predominant extrapituitary (800 nucleotide) message, while in tissues known to express the normal pituitary (1150 nucleotide) message and longer species, a tendency towards undermethylation was observed. Although the sites at which variable methylation occurs did not correspond to established binding sites for regulatory proteins, many of these regions remain to be determined and thus it is possible that methylation may be influential in the tissue-specific regulation of this gene.

It has previously been shown that interleukin-1 (IL-1) directly stimulates the release of CRH-41 from rat hypothalamus in vitro, suggesting that cytokines may mediate the effects of changes in immune state on the hypothalamo-pituitary adrenal axis (HPA). However, it is likely that several cytokines can cause changes in neuroendocrine function, and we have now investigated a series of others for central activity on the HPA: IL-2, IL-6, IL-8, tumor necrosis factor (cachectin), interferon-alpha 2, and interferon-gamma. The static rat hypothalamic incubation system used involves fresh hypothalamic explants with consecutive 20-min incubation, and estimation of CRH-41 concentrations in the medium by a specific RIA; the acute effects of cytokines on ACTH release from rat dispersed pituitary cells were also measured. IL-6 increased hypothalamic CRH-41 secretion in the range 10-100 U/ml, but had no effect on isolated median eminences incubated in vitro under the same conditions. IL-6 (1-1000 U/ml) also had no effect on the secretion of ACTH from freshly dispersed rat anterior pituitary cells when administered in 10-min pulses. The effects of both IL-1 and IL-6 were antagonized by blockade of the eicosanoid cyclooxygenase pathway, but not by lipooxygenase blockade. Neither IL-2 (1-10000 U/ml), IL-8 (0.1-10 nM), tumor necrosis factor (10-1000 U/ml), interferon-alpha 2 (10-1000 U/ml) nor interferon-gamma (10-1000 U/ml) had any effect on hypothalamic CRH-41 release or pituitary ACTH release. It is therefore concluded that IL-6, like IL-1, can exert a potent enhancing effect on the HPA by acutely stimulating the secretion of CRH-41 from the hypothalamus at a site above the level of the median eminence, at concentrations known to occur in human plasma and cerebrospinal fluid. These effects are probably mediated by cyclooxygenase products. Acute stimulatory effects of the other cytokines investigated on the HPA are unlikely to be exerted through changes in either CRH-41 or ACTH directly.

Many peripheral tissues express the proopiomelanocortin (POMC) gene as an 800-base mRNA that lacks the 5' end of the 1200-base pituitary transcript. The missing region encodes the peptide signal sequence, and thus, it is unlikely that any translation product would be secreted. We have found that a RNA transcript equivalent to this short message, generated by transcription in vitro from a T7 polymerase promoter, is translatable in a rabbit reticulocyte lysate, generating peptides of 27.5, 22.5, and 15.5 kD. None of these peptides appears to be processed or protected from proteinase-K digestion by a microsomal membrane fraction. In vivo studies were undertaken by transfecting into GH3 cells one of two expression vectors containing sequences that would produce either a full-length mRNA or a short (800-base) mRNA. The neomycin resistance gene was cotransfected with these plasmids, and 30 permanent cell lines were produced after selection in G418. Cell lines containing the full-length RNA secreted large quantities of ACTH and beta-endorphin immunoreactivity, whereas those expressing the short transcript secreted neither of these peptides. However extractable peptide was present in this latter type of cell line, thereby suggesting that the 800-base mRNA was translated, and that no peptide reached the secretory vesicle. These findings raise important questions about the role of peripheral POMC gene expression.

It has been suggested that melanin concentrating hormone (MCH) possesses potent corticotrophin (ACTH) inhibitory activity, on the basis of the inhibitory effects displayed by salmon MCH on ACTH release from either trout or rat isolated pituitary fragments. Recently, rat MCH has been characterised, and this prompted us to investigate the putative inhibitory activity of synthetic rat MCH on basal and stimulated ACTH secretion from freshly-dispersed rat pituitary cells or incubated rat pituitary fragments, as well on KCl (28 mmol/l) or noradrenaline-evoked release of corticotrophin releasing hormone-41 (CRH-41) from rat hypothalamic explants in vitro. There were no effects of rat MCH on either CRH-41 or ACTH release in vitro.

Atrial natriuretic peptide, ANP(99-126), is derived from cardiac atrial tissue and has potent effects on salt and water homeostasis, including the inhibition of aldosterone and vasopressin release. Recent studies have also suggested that it may suppress the pituitary-adrenal axis. In addition, N-truncated forms of ANP, such as ANP(103-126), have been identified within the central nervous system, with a prominent hypothalamic localization in the paraventricular nucleus. We have therefore investigated whether ANP(99-126) and ANP(103-126) are able to modulate the release of the principal ACTH-releasing factor, corticotrophin-releasing factor-41 (CRF-41), from the rat hypothalamus in vitro. The static incubation system has been previously described in detail. Male Wistar rats were decapitated between 09.00 and 09.30 h, their hypothalami rapidly removed, and four half-hypothalami incubated for 20-min intervals following a period of stabilization. The effect of the ANP peptides on the basal (B) and KCl (28 mmol/l)-stimulated (S) release of immunoreactive CRF-41 was studied by means of successive incubations in the absence (B1, S1) and presence (B2, S2) of the peptides. The ratios B2:B1 and S2:S1 were compared with parallel control incubations by ANOVA. Neither form of ANP had any effect on the basal release of CRF-41. ANP(99-126) caused a dose-dependent inhibition of CRF-41 release in the concentration range 1-100 nmol (P less than 0.01). ANP(103-126) also suppressed the release of CRF-41 in the concentration range 100 pmol/l-100 nmol/l (P less than 0.01), with a minimum S2:S1 ratio at 10 nmol/l, and a decrease in effect at 100 nmol/l. Finally, the stimulation of CRF-41 release induced by noradrenaline (10 nmol/l and 1 mumol/l) was non-competitively antagonized by 100 nmol ANP(99-126)/l and 10 nmol ANP(103-126)/l.(ABSTRACT TRUNCATED AT 250 WORDS)

We have previously shown that the release of corticotrophin-releasing factor 41 (CRF-41) induced by a variety of neurotransmitters and depolarizing agents from the rat hypothalamus in vitro is inhibited by morphine. In order to further characterize the opiate receptors mediating this inhibitory action, we have now investigated the effects of a variety of opioid compounds with relatively high selectivity for mu-, kappa- and delta-opiate receptors on K(+)-stimulated CRF-41 release. The selective mu-opioid receptor agonist 202-250 inhibited K(+)-evoked CRF-41 release in a dose-dependent manner with a maximum inhibition of approximately 60% at 10(-5) M (p less than 0.01), as did the kappa-selective agonists PD-117,302 and U-50,488, with a similar plateau in response of approximately 40% inhibition at 10(-6) M (p less than 0.05). The effects of these agonists were specifically reversed by the mu- and kappa-receptor antagonists naloxone and MR2266, respectively, while the specific delta-receptor antagonist ICI 154,129 was ineffective. Both naloxone and MR2266 slightly but significantly increased the basal release of CRF-41. The delta-agonist D-Pen2,5-enkephalin was without significant effect in the same dose range. These data suggest that both mu- and kappa-receptors, but not delta-receptors, mediate the inhibitory effect of opiates on stimulated CRF-41 release from the rat hypothalamus.

Abstract There is increasing evidence for a centrally mediated inhibitory effect of the amino-acid neurotransmitter y-aminobutyric acid (GABA) on the hypothalamo-pituitary-adrenal axis. In the present study, the direct effect of GABA in modulating the release of the 41-residue corticotrophin-releasing factor (CRF-41), the major CRF identified so far, was investigated in acute hypothalamic explants by utilizing previously validated incubation and assay techniques. While GABA (10(-7)'to 10(-5) M) had no effect on basal CRF-41 release (P > 0.05), it significantly suppressed K (-) (28 mM)-stimulated release in a dose-dependent manner (P < 0.01). A similar inhibitory effect was observed with the GABA agonist muscimol (10(-7) to 10(-5) M). Noradrenaline (10(-6) M) -induced CRF-41 release was also significantly inhibited by GABA 10(-6) M. The inhibitory effect of GABA on K(+)-stimulated CRF-41 secretion was completely. reversed by the GABA antagonists bicuculline and picrotoxin (10(-6) to 10(-5) M) in a dose-dependent fashion. Both bicuculline and picrotoxin stimulated basal and K(+) (28 mM)-stimulated CRF-41 release, indicating the presence of tonic inhibition by endogenous GABA in the basal state. Finally, GABA 10(-5) M was able to significantly inhibit the stimulated release of CRF-41 from the isolated median eminence. In summary, the present data provide strong evidence that GABA-induced inhibition of the hypothalamo-pituitary-adrenal axis is mediated, at least in part, through an inhibitory action on CRF-41 secretion. It is likely that these GABA receptors are located directly on CRF-41 neurons, probably on nerve terminals in the median eminence.

Hemodynamic changes induced by a single, total paracentesis were evaluated in 21 patients with tense ascites from whom 4 to 16 L of ascites were drained over 2 to 8 hr with no serious complications. At 60 min, compared to baseline, there was an increase in cardiac output (7.7 +/- 0.5 to 8.5 +/- 0.6 L/min, p less than 0.02) and a tendency for right atrial pressure to decrease (9.3 +/- 0.8 to 7.50 +/- 0.8 mm Hg, NS), with no change in pulmonary capillary wedge pressure (10.9 +/- 0.9 to 10.7 +/- 0.9 mm Hg). Between 3 and 12 hr later, there was a drop in right atrial pressure, pulmonary capillary wedge pressure and cardiac output to 5.6 +/- 0.6 (p less than 0.02), 7.2 +/- 0.8 mm Hg (p less than 0.002) and 7.2 +/- 0.6 L/min (NS) respectively, indicative of the development of relative hypovolemia and suggesting that therapeutic plasma expansion is appropriate at this time. Two-dimensional echocardiography before paracentesis (n = 8) showed a reduction in the right to left atrium area ratio as compared with values in patients with minimal ascites (0.54 +/- 0.04 vs 0.82 +/- 0.02, p less than 0.0001). This technique may help in identifying patients with right atrial compression caused by tense ascites.

A human small cell lung cancer cell line (COR L103) that actively expresses the proopiomelanocortin (POMC) gene has been used as a model of extrapituitary ACTH-secreting tumors to investigate the phenomenon of resistence of ACTH production to glucocorticoids. After both short term (24 h) and long term (10 days) exposure to hydrocortisone at concentrations of 500 and 1000 nM, the accumulation of intracellular POMC mRNA, ACTH, and ACTH precursor peptides in the culture medium was not suppressed. These finding contrast with those in the pituitary corticotroph cell line AtT20, in which POMC mRNA, ACTH, and ACTH precursors were suppressed under the same conditions. Two other genes that are regulated by glucocorticoids in other cell types, the tyrosine amino transferase gene and the glucocorticoid receptor gene, were expressed in COR L103 cells. However, neither gene appeared to be regulated by hydrocortisone in this small cell lung cancer cell line. Further studies demonstrated that glucocorticoid receptor binding could be detected in the nucleus and cytoplasm, with a Kd of 5 X 10(-9) M. It is concluded that nonsuppression of POMC by glucocorticoids is probably part of a more global defect of glucocorticoid signaling in these cells, but that this defect lies distal to steroid binding in the nucleus.

The acute effects of submaximal endurance exercise (three consecutive 20-min runs on a treadmill at 50, 60 and 70% of the subjects' maximum oxygen uptake) upon the pulsatile release of LH were compared with those accompanying leisurely strolling for a similar period in seven normally menstruating young women. All trials were conducted during the early to mid-luteal phase, as determined by body temperature patterns, ultrasonic scans of the ovaries, detection of the LH surge in first morning urine specimens, and serial measurements of plasma progesterone. Blood was sampled every 10 min via an indwelling cannula for 8 h before and 12 h after exercise and serum LH measured by radioimmunoassay. LH pulsations were analysed by a time series method. Following cannulation, mean LH levels declined but then rose to reach a maximum 2 h before the beginning of the exercise bout. LH concentrations remained virtually unchanged during exercise itself, and exhibited a declining trend throughout the post-exercise period. The findings in the two groups were similar in all respects, except that in the control study the rate of LH pulsatility was significantly diminished (P less than 0.05) during the first 2 h of sampling as compared with the subsequent 2-h period. The approximate half-life of LH varied from 27 to 57 min, with a mean of 41 min.

Endogenous opioid peptides have been implicated in the pathophysiology of shock (1-5). In anaesthetised mongrel dogs, administration of E coli endotoxin caused a rise in plasma met-enkephalin-like immunoreactivity (MLI). Biochemical characterisation of MLI by gel filtration chromatography revealed various molecular forms: 31K, 8K, 3-5K and the native pentapeptide in approximately equal amounts. After enzymatic treatment of column fractions the 31K form predominated (90.7%). This is the first demonstration of elevated MLI in endotoxin shock.

A chromatographic procedure has been developed for the characterization of ACTH- and lipotrophin- (LPH) related peptides in human plasma under acid-dissociating conditions to minimize artifacts of protein binding. The recovery and sensitivity of this method permits identification of ACTH at normal physiological levels in the circulation. Plasma profiles obtained from normal subjects and patients with pituitary dependent Cushing's disease, Addison's disease and Nelson's syndsrome showed only one significant peak of ACTH activity eluting in the position of purified native human 1--39 ACTH. However, the plasma profiles obtained from all the patients with the ectopic ACTH syndrome demonstrated a second peak of immunoreactive larger-molecular-weight ACTH and in some plasma samples this was the only form of ACTH observed. This larger-molecular-weight ACTH eluted midway between the void volume and 1--39 ACTH and co-eluted with a protein marker of molecular weight 22 000.

A patient is described with tumours in the region of the pineal gland and anterior hypothalamus associated with high levels of hCG beta in the serum and cerebrospinal fluid (CSF). He presented aged 19, with hypopituitarism, but persistent secondary sexual characteristics. LH immunoreactivity in serum was due to the hCG beta which probably caused the elevated level of testosterone. Following cranial irradiation the tumour became undetectable and hCG beta was eradicated from the serum and CSF. The patient later died because of an intramedullary metastasis of choriocarcinoma in the cervical spinal cord. The endocrine details of six previously reported intracranial neoplasms which have been shown to secrete hCG beta are reviewed. Only two of these involved the pineal region. Chorionic gonadotrophin production by this tumour enabled early detection of its recurrence. It is unclear how often precocious puberty is caused by tumours producing hCG beta, but patients presenting either with that problem or a pineal tumour should have circulating hCG beta measured.

Serum testosterone, sex hormone binding globulin (SHBG) and prolactin were measured in thirty-eight women with acne which persisted or started after the age of 18 years. One or more of these levels were abnormal in 76% of patients. Increased testosterone or low SHBG were present alone or in combination in 60% of patients. This group was presumed to have a raised level of non-protein bound, metabolically-available testosterone. Hyperprolactinaemia, which was present in 45% of patients, may be important in view of the reported association with increased adrenal androgens. The hormonal abnormalities may be causally related to the acne and a greater understanding of them may lead to better treatment.

We have previously reported that in normal subjects plasma immunoreactive somatostatin levels rise after a mixed meal. The contribution of individual nutrients to this rise, and the molecular nature of the somatostatin immunoreactivity measured, have now been studied. Six normal healthy subjects received, on separate occasions, isocaloric (520 calories) and isovolumetric (260 ml) quantities of carbohydrate, protein, and fat. The mean fasting plasma somatostatin level was 29 +/- 5 pg/ml. After carbohydrate a peak of 48 +/- 7 pg/ml was reached at 30 min, and after protein and fat there were more sustained rises with peak levels of 74 +/- 8 pg/ml and 80 +/- 9 pg/ml, respectively. Sephadex G50 chromatography of extracts of fasting peripheral plasma showed two main peaks of somatostatin immunoreactivity, one coeluting with cyclic somatostatin and a larger peak of approximately 3500 molecular weight (mol wt). Levels of both 1600 and 35000 mol wt somatostatin were increased 60 min after a mixed meal. Approximately 80% of the 3500 mol wt form of somatostatin could be converted to the 1600 mol wt form by treatment with dithiothreitol (an agent which reduces disulphide bonds). It is concluded that: (a) in normal subjects fat and protein are potent stimuli for somatostatin release; (b) somatostatin in normal peripheral plasma exists in multiple forms, and that both 1600 and 35000 mol w forms of somatostatin immunoreactivity are stimulated by feeding; (c) the 3500 mol wt form could represent a dimer of somatostatin or a somatostatin molecule linked to a second peptide chain by disulphide bonds.

Thirteen patients with either Addison's disease, or Cushing's disease treated by bilateral adrenalectomy, were infused with the long-acting met-enkephalin analogue DAMME. In patients with Addison's disease significant and pronounced falls in ACTH and N- and C-terminal beta-LPH were seen; chromatography suggested that beta-endorphin fell concomitantly. Three out of four patients with Cushing's disease who had not received pituitary irradiation, also showed a decrease in plasma ACTH and N- and C-terminal beta-LPH; however, no change was seen in any of the irradiated patients. The changes were naloxone reversible. The levels of plasma met-enkephalin were normal and did not change after DAMME in any group of patients. These results are interpreted as suggesting that there are inhibitory opiate receptors controlling the release of ACTH, beta-LPH, and beta-endorphin.

The established technique of dynamic perfusion of dispersed rat anterior pituitary cells was used to investigate the role of dopamine in the release of thyroid-stimulating hormone (TSH). The basal release of TSH was 124 +/- 22 ng/ml (mean +/- SEM) and this remained unchanged in the presence of dopamine (5 X 10(-6) M), while basal prolactin release was suppressed to 50% of control values. Perfusion with thyrotrophin-releasing hormone (TRH) in doses between 1.4 X 10(-10) and 22.4 X 10(-10) M produced a consistent and reproducible dose-response curve for TSH (n = 14) which was not significantly altered by the presence of dopamine (n = 5). Perfusion with bromocriptine (10(-6) M), a dopamine agonist, did not alter the basal or stimulated TSH release. No stimulation of TSH release was observed when the cells were challenged with 2-min pulses of domperidone, a dopamine antagonist (2 X 10(-9) to 2 X 10(-5) M). The inclusion of somatostatin-14 (3 X 10(-9) M) in the perfusate inhibited TRH-stimulated TSH release. Our results suggest that, in the rat, dopaminergic inhibition of TSH release does not occur at the level of the pituitary.

Pituitary regulation of gonadal function was investigated in 39 consecutive men with treated and untreated coeliac disease and in an intestinal disease control group of 19 men with Crohn's disease of similar age and general nutritional status. Basal serum FSH concentration was increased in 10 of the coeliacs (26%) compared to only two of 19 men with Crohn's disease (11%). This abnormality was observed with equal frequency in both treated and untreated coeliacs, and was not associated with oligospermia. Serum LH concentration was increased in eight of 15 untreated coeliacs (53%) with sub-total villous atrophy, an abnormality which unlike the elevation of serum FSH, appears to return towards normal after gluten withdrawal. Serum LH was high in coeliacs despite marked elevation of the free testosterone index. Exaggerated responses of FSH and LH to LHRH were found in 89% and 45% respectively, of coeliacs with sub-total villous atrophy. However, exaggerated responses of LH alone were found more frequently in coeliacs than in men with Crohn's disease (P less than 0.02) and unlike the exaggerated FSH responses, LH responses were closely related to jejunal morphology. Exaggerated responses of FSH and LH in coeliacs were commonly found when basal gonadotrophin concentrations were normal. The occurrence of exaggerated gonadotrophin responses could not be related to plasma concentration of testosterone, dihydrotestosterone, oestradiol or the free testosterone index. Serum prolactin was modestly raised in 25% of untreated and partially treated coeliacs and in the same proportion of men with Crohn's disease. Elevated serum prolactin concentrations never exceeded 809 mU/l and were not associated with impotence or infertility. This study provides further evidence that in men with coeliac disease there is a derangement of pituitary regulation of gonadal function. This would seem to be part of a wider disturbance of central regulatory mechanisms of endocrine function in coeliac disease.

Basal and stimulated secretion of N-terminal pro-opiocortin (Pro-gamma-MSH), ACTH and LPH from seven pituitary and three ectopic ACTH secreting tumours have been studied in vitro using a perfused isolated cell system. The peptides were shown to be released concomitantly and in equimolar amounts. The pituitary tumours responded to stimulation with rat stalk median eminence extracts (SME) and synthetic AVP. However, peptide release from the ectopic tumours, although pulsatile, remained autonomous. Prior to surgery, gel-chromatographic profiles of plasma immunoreactive ACTH showed only one peak, which eluted in the position of 1-39 ACTH, in patients with the pituitary tumours, but there was a second peak of large molecular weight ACTH present in the plasma from those with the ectopic ACTH syndrome. This second form of ACTH could not be detected in any of the tumour cell column effluents. An eighth pituitary tumour was atypical, in its unusually large size, clinically aggressive nature and spectrum of peptide release. Although peptide release in response to stimulation with SME was similar to that observed with the other pituitary tumours, the chromatography of the plasma ACTH resembled the ectopic plasma pattern, showing two peaks of immunoreactivity.

Expression of the RNA coding for the ACTH-beta-lipotrophin precursor, pro-opiomelanocortin (POMC), has been demonstrated in five human small-cell lung cancer (SCLC) cell lines. Using Northern and slot-blot hybridization analysis of RNA and a bovine POMC cDNA as probe, the processed POMC RNA from SCLC cells was found to be approximately 1350 nucleotides in length, which is larger than that found in the normal human pituitary. Expression of the POMC gene was confirmed by measurement of ACTH precursors secreted by the cells, using a novel two-site immunoradiometric assay based on monoclonal antibodies, which directly quantifies both POMC and pro-ACTH but does not recognize ACTH. Levels of POMC in medium accumulated throughout the growth of the cells, in contrast to POMC RNA which showed a relatively constant level of expression. We conclude that human SCLC cell lines are valuable models for studying the aberrant expression and regulation of the human POMC gene.